mouth off

US /maʊθ ɔf/
UK /maʊθ ɔf/
"mouth off" picture
1.

дерзить, грубить

to speak in an insolent or disrespectful way, especially to someone in authority

:
He got fired for mouthing off to his boss.
Его уволили за то, что он дерзил своему начальнику.
Don't mouth off to your elders.
Не дерзи старшим.